State environmental officials this week notified Northrop Grumman of an investigation into claims that buried drums were discovered in the 1990s and subsequently covered up on land that the defense contractor’s predecessor donated to Oyster Bay Town.

Grumman Aircraft Engineering Corp., which became Northrop Grumman, turned the 18-acre parcel over to the town in 1962, which converted it into Bethpage Community Park. Grumman had used the land to legally dispose of rags, paints, chromium-tainted sludge, arsenic and other solvents.

The Department of Environmental Conservation earlier this month opened an investigation after a whistleblower came forward about what he witnessed at the park off Stewart Avenue.

“[W]e are investigating a recent tip that barrels of waste may have been disposed of and covered in the 1990s in the Bethpage Community Park . . . ,” DEC acting Commissioner Basil Seggos wrote in an April 20 letter. “We expect Northrop Grumman’s full cooperation in addressing that issue.”

The passage was included in a letter relating to an $81 million Superfund cleanup plan for the park to remove soil contamination and remediate a groundwater plume emanating from the site.

Northrop Grumman spokesman Vic Beck said in a statement that the state had informed the defense contractor of the probe “and we will cooperate fully, just as we have done for over 20 years.”

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Newsday reported the DEC investigation Monday evening, and on Wednesday the Town of Oyster Bay closed down a playground area and tennis courts plus a nearby grassy area.

The town later blocked off additional areas, including the community pool not yet open for the season, a picnic area between the pool and playground, and a grassy area adjacent to basketball and handball courts. It also fenced off a gravel spot between the playground and ballfields, which have been fenced off for more than a decade because of contaminated soils.

Town spokesman Brian Devine said the additional areas were closed because they provided access, though roundabout, to the playground and tennis court areas. The move was an “extra precaution,” he said.

Town Supervisor John Venditto praised DEC’s response, calling it exemplary. “We would welcome Grumman’s cooperation,” he said. “The sooner we resolve this issue brought up by the tipster the sooner we can get back to the quiet, peaceful enjoyment of our park.”

The park has a long history of contamination, remediation and excavation. It was once part of a more than 600-acre campus home to aviation design, testing and manufacturing operations for the Navy and Grumman between the 1930s and 1990s.

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Contaminated water was documented in 1947, volatile organic chemicals came later, and in 1983 the campus was added to the state’s Superfund cleanup program for hazardous waste sites. Several cleanup plans exist to treat on-site and off-site contamination plumes.

At a public meeting this week hosted by the Navy, DEC Director of Environmental Remediation Robert Schick said about 11 acres of the park had been remediated over the years and drums were found at one point.

“We are still hoping to get better determination from the whistleblower as to where he believes the drums are because during the course of the remediation and excavation we undertook, they did identify an area that had drums,” Schick said. “Most of them appeared to be empty but we did identify and remove those.”

Town spokeswoman Marta Kane said during excavation work for the ice rink in 2006/2007, drums were discovered and “they were crushed drums which were not believed to hold any contaminants.”